"SerialOutput - Mavlink" - connection status not showing; adding a connections panel

#### Issue details
When mirroring the Mavlink Stream (from the temp screen/ Ctrl-F), the resulting window (Port, Speed) has a "Connect" button.
Once pushed, the connection is (likely) initiated - but the button keeps showing "Connect".

The user is left in the dark if the connection was successful or not - and how to stop it.

If this box is closed and the dialog called up again, the resulting popup window now shows a "Stop" button. But also which connection _is_ actually running, i.e. which one can now be stopped, is not clear from that dialog, since the drop down fields both don't show an entry.

Expected behavior:
1. Connect button changes to show "Stop" upon successful connection
2. Active connection is displayed (in drop-down) when calling up the dialog again.

It would also be _very_ nice, if _all_ the various connections which can be initiated/ received and managed by MP (primarily from Ctrl-F), with their ports, directions, speed, connection status and throughput would be listed, combined and managed in ONE clean, collapsible/ configurable panel (be they MAVlink, COMport forwarding, serialpass or gps inject).

This would provide a much cleaner and clearer overview to the user of the current status.
Since flight safety and precision can be involved here, this area should not be scattered and ambiguous.

Thanks for considering this!
#### Version
1.36.2

Start from the “SerialOutput - Mavlink” dialog described in the issue and reproduce the connection workflow from the temporary screen/Ctrl-F. Verify that a successful connection changes “Connect” to “Stop” and that reopening the dialog identifies the active connection. The broader panel should list and manage the connection details and statuses named in the issue.

Written by the indexing model from the issue text.